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Old 09-11-2019, 10:59 AM
Fotheringay-Phipps is offline
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Loose A/C adapter cuts power to the line(s)


I just had a scare of sorts when the outlets powering my freezer and spare fridge in the garage stopped working. Also, the outlets in the upstairs bathrooms. I checked all the circuit breakers and the GFI outlets (I only know of two, in the kitchen) and everything was in order. I was getting recommendations for electricians when my wife came home and saved the day.

We have an intercom system which gets power through a couple of a/c adapters plugged into an outlet in the basement (I think one might be for the intercom and one for the remote door unlock), and she remembered that once when these come loose, it cut off power to a bunch of outlets. And so it was. Both of the adapters were loose (we've had a few little kids staying in that room the past few days ) and when we pushed these back in everything went back on.

Questions are:
  • Why should this be so (IOW, what's happening from a technical perspective)?
  • Is this some sort of incorrect design (by either the guy who wired the house or the guy who did the intercom)? And,
  • Could this be changed at this point to prevent it from happening again?
  #2  
Old 09-11-2019, 11:19 AM
bob++ is offline
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I have no idea why a loose adapter should cut off the power, but you should have a serious think about whether that setup is okay where "little kids" can get to them.
  #3  
Old 09-11-2019, 11:37 AM
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IANAElectrician, but if the circuit breakers and GFIs weren't the root cause, I would be very concerned indeed. I have no idea who screwed what up or how, but at the bare minimum I would get a professional in to look at things, were I in your situation. That just plain don't sound right.
  #4  
Old 09-11-2019, 11:59 AM
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Quote:
Originally Posted by Fotheringay-Phipps View Post
I just had a scare of sorts when the outlets powering my freezer and spare fridge in the garage stopped working. Also, the outlets in the upstairs bathrooms. I checked all the circuit breakers and the GFI outlets (I only know of two, in the kitchen) and everything was in order. I was getting recommendations for electricians when my wife came home and saved the day.

We have an intercom system which gets power through a couple of a/c adapters plugged into an outlet in the basement (I think one might be for the intercom and one for the remote door unlock), and she remembered that once when these come loose, it cut off power to a bunch of outlets. And so it was. Both of the adapters were loose (we've had a few little kids staying in that room the past few days ) and when we pushed these back in everything went back on.

Questions are:
  • Why should this be so (IOW, what's happening from a technical perspective)?
  • Is this some sort of incorrect design (by either the guy who wired the house or the guy who did the intercom)? And,
  • Could this be changed at this point to prevent it from happening again?
I'd wager the outlet (receptacle) the adapters are plugged into is physically broken in some way and jostling the adapters cuts power to the downstream receptacles. This is a potentially hazardous situation; if it's a poor connection or broken conductor then you risk it overheating or arcing and causing a fire. inspect that receptacle ASAP (or call an electrician if you're not comfortable doing it yourself.)

edited to add: yes, you can have multiple receptacles on one branch circuit, that's one reason they have two sets of screws for attaching wires on the sides.

Last edited by jz78817; 09-11-2019 at 12:01 PM.
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Old 09-11-2019, 02:50 PM
Tim@T-Bonham.net is offline
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Quote:
Originally Posted by jz78817 View Post
I'd wager the outlet (receptacle) the adapters are plugged into is physically broken in some way and jostling the adapters cuts power to the downstream receptacles. This is a potentially hazardous situation; if it's a poor connection or broken conductor then you risk it overheating or arcing and causing a fire. inspect that receptacle ASAP (or call an electrician if you're not comfortable doing it yourself.)
Yes, that's quite possible. When you re-plugged the adapters, you wiggled the loose wires enough to bring the circuit back. You might try checking that receptacle to see if it feels warm. (When the adapters are unplugged -- those often are warm.) Try wiggling the receptacle and see if the later circuit goes on & off. And yes, this is a situation that should be attended to soon.

Quote:
Originally Posted by jz78817 View Post
edited to add: yes, you can have multiple receptacles on one branch circuit, that's one reason they have two sets of screws for attaching wires on the sides.
That's called daisy-chain wiring. It's not a recommended practice any more, because of this possibility -- all the power runs through the receptacle, and a loose wire here cuts off power to all later devices on the circuit. Instead, current recommended practice is to have short (6-8 inch) pigtail wires on the receptacle, and connect them with wire nuts to the power cables in the box.
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Old 09-12-2019, 12:49 PM
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Quote:
Originally Posted by Tim@T-Bonham.net View Post
Yes, that's quite possible. When you re-plugged the adapters, you wiggled the loose wires enough to bring the circuit back. You might try checking that receptacle to see if it feels warm. (When the adapters are unplugged -- those often are warm.) Try wiggling the receptacle and see if the later circuit goes on & off. And yes, this is a situation that should be attended to soon.
I agree but would suggest that instead of attending to this soon it should be attended to ASAP.

Quote:
That's called daisy-chain wiring. It's not a recommended practice any more, because of this possibility -- all the power runs through the receptacle, and a loose wire here cuts off power to all later devices on the circuit. Instead, current recommended practice is to have short (6-8 inch) pigtail wires on the receptacle, and connect them with wire nuts to the power cables in the box.
Do you have a cite for this?
I haven't seen any info that says daisy chain wiring is contrary to best practices. I don't see how wire nuts could be significantly better in reliability than the terminal connections on a standard outlet.
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Old 09-12-2019, 01:33 PM
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To those who seem to be suggesting that this presents some sort of safety issue: Suppose I simply replace the outlet/receptacle with a new one, does this take care of whatever potential safety issues are being contemplated (and if the problem still exists, then it's a weird design thing and not a possibly dangerous malfunction) or is there possibly some other dangerous malfunction which would not be fixed by replacing the outlet?
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Old 09-12-2019, 01:41 PM
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Quote:
Originally Posted by BubbaDog View Post
I agree but would suggest that instead of attending to this soon it should be attended to ASAP.



Do you have a cite for this?
I haven't seen any info that says daisy chain wiring is contrary to best practices. I don't see how wire nuts could be significantly better in reliability than the terminal connections on a standard outlet.
I second the motions.

Is it considered best practice to run a cable to each outlet, or use pigtails and wire nuts?
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Old 09-12-2019, 01:49 PM
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Quote:
Originally Posted by BubbaDog View Post
Do you have a cite for this?
I haven't seen any info that says daisy chain wiring is contrary to best practices. I don't see how wire nuts could be significantly better in reliability than the terminal connections on a standard outlet.
The NEC allows either practice, as long as the receptacle is UL listed for carrying the downstream current. (Basically anything you get in a big-box or reputable hardware store will be. Shady Amazon and eBay sellers may be a different story.)

I agree that it is more convenient for future work to do pigtails, especially if you need to temporarily remove a broken receptacle while you go scrounge up a replacement. If you want to keep the downstream loads alive while the old receptacle is missing, you would have to temporarily splice the two sides of the branch circuit together. With pigtails, just cap off the dangling tail for safety and the rest of the circuit still works.

ETA: The disadvantage is it's more work initially, and requires more wire nuts and space in the box.

Last edited by friedo; 09-12-2019 at 01:51 PM.
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Old 09-12-2019, 01:57 PM
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Quote:
Originally Posted by Fotheringay-Phipps View Post
To those who seem to be suggesting that this presents some sort of safety issue: Suppose I simply replace the outlet/receptacle with a new one, does this take care of whatever potential safety issues are being contemplated (and if the problem still exists, then it's a weird design thing and not a possibly dangerous malfunction) or is there possibly some other dangerous malfunction which would not be fixed by replacing the outlet?
The problem is likely to be loose or broken wires in the box where the receptacle is. Replacing it should solve the problem. In fact, just opening the box and taking it out will probably identify the problem -- might just need tightening the wires on the current receptacle to fix the problem.
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Old 09-13-2019, 11:34 AM
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Quote:
Originally Posted by friedo View Post
The NEC allows either practice, as long as the receptacle is UL listed for carrying the downstream current. (Basically anything you get in a big-box or reputable hardware store will be. Shady Amazon and eBay sellers may be a different story.)

I agree that it is more convenient for future work to do pigtails, especially if you need to temporarily remove a broken receptacle while you go scrounge up a replacement. If you want to keep the downstream loads alive while the old receptacle is missing, you would have to temporarily splice the two sides of the branch circuit together. With pigtails, just cap off the dangling tail for safety and the rest of the circuit still works.

ETA: The disadvantage is it's more work initially, and requires more wire nuts and space in the box.
Thanks friedo
I just replaced nearly every receptacle in my house. (Mrs BD changed the color scheme from almond to white). Although the receptacles were old and in some cases worn the wire terminals were in good shape and I saw no evidence (voltage drop) that the downstream circuit was affected.
It's hard enough to have room for two cables in those small boxes. It seems to me that adding pigtails and wire-nuts would just invite more opportunity for a bad connection.
My apologies to Fotheringay-Phipps for the side-jack. I agree with Tim@T-Bonham.net that the first thing to do to solve the problem is to examine the integrity of the adapter outlet.
Either hire an electrician or, if you are mechanically inclined -
Turn off the breaker
Test the receptacle to be sure that you killed the correct circuit.
Examine the receptacle
Tighten loose connection or replace the receptacle.

In any case - this is something that you need to do ASAP. The situation you have described is scary. You have high current use downstream of this receptacle as proven by the outages to you fridge and freezer. High current + poor connection = heat and fire hazard.
I'm sorry if that scares you unnecessarily but this is a situation where its best to play it safe.
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